Letrozole is used treat early breast cancer in women who have experienced menopause (change of life; end of monthly menstrual periods) and who have had other treatments, such as radiation or surgery to remove the tumor. It is also used to treat early breast cancer in women who have experienced menopause and who have already been treated with a medication called tamoxifen (Nolvadex) for 5 years. Letrozole is also used in women who have experienced menopause as a first treatment of breast cancer that has spread within the breast or to other areas of the body or in women whose breast cancer has worsened while they were taking tamoxifen. Letrozole is in a class of medications called nonsteroidal aromatase inhibitors. It works by decreasing the amount of estrogen produced by the body. This can slow or stop the growth of some types of breast cancer cells that need estrogen to grow.

Letrozole comes as a tablet to take by mouth once a day with or without food. Take letrozole at around the same time every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take letrozole exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

You may need to take letrozole for several years or longer. Continue to take letrozole even if you feel well. Do not stop taking letrozole without talking to your doctor.

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Before taking letrozole,

• Tell your doctor and pharmacist if you are allergic to letrozole, any other medications, or any of the ingredients in letrozole tablets. Ask your pharmacist for a list of the ingredients.
• Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: medications that contain estrogen such as hormone replacement therapy (HRT) and hormonal contraceptives (birth control pills, patches, rings, and injections); raloxifene (Evista); and tamoxifen (Nolvadex).
• Tell your doctor if you have high cholesterol, osteoporosis (condition in which the bones are fragile and break easily), or liver disease.
• You should know that letrozole should only be taken by women who have experienced menopause and cannot become pregnant. However, if you are pregnant or breast-feeding, you should tell your doctor before you begin taking this medication. Letrozole may harm the fetus.
• You should know that letrozole may make you drowsy. Do not drive a car or operate machinery until you know how this medication affects you.

Unless your doctor tells you otherwise, continue your normal diet.

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Letrozole may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• Hot flushes
• Night sweats
• Nausea
• Vomiting
• Loss of appetite
• Constipation
• Diarrhea
• Heartburn
• Stomach pain
• Changes in weight
• Muscle, joint, or bone pain
• Excessive tiredness
• Headache
• Dizziness
• Weakness
• Swelling of the hands, feet, ankles, or lower legs
• Difficulty falling asleep or staying asleep
• Vaginal bleeding or irritation
• Breast pain
• Hair loss
• Blurry vision

Some side effects can be serious. If you experience any of these symptoms call your doctor immediately or get emergency medical treatment:

• Chest pain
• Rash
• Hives
• Itching
• Difficulty breathing
• Unusual bleeding or bruising
• Pain in the upper right part of the stomach
• Yellowing of the skin or eyes
• Flu-like symptoms
• Pain, warmth, or heaviness in the back of the lower leg
• Severe headache
• Sudden speech problems
• Sudden weakness or numbness of an arm or leg

Letrozole may cause or worsen osteoporosis. It can decrease the density of your bones and increase the chance of broken bones and fractures. Talk to your doctor about the risks of taking this medication.

Letrozole may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your body’s response to letrozole.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.